The present invention relates generally to motor vehicle alignment and, more specifically, to providing a target system for obtaining positional information regarding positions on a vehicle using a position determination system.
Motor vehicle alignment systems are important for ensuring that the alignments of wheels on a vehicle are within the specifications provided by motor vehicle manufacturers. If the wheels are out of alignment, there may be excessive or uneven wear. In addition, the performance of the vehicle, particularly handling and stability, may be adversely affected if the wheels are not properly aligned. As used herein, the term xe2x80x9cwheelxe2x80x9d or xe2x80x9cvehicle wheelxe2x80x9d refers to the tire and wheel assembly found on a motor vehicle. Such an assembly generally includes a conventional tire that is mounted on a metal wheel or xe2x80x9crim.xe2x80x9d
The wheels of a motor vehicle may be aligned in a number of ways. For example, an operator or an alignment technician can use a vision imaging system such as a computer-aided, three-dimensional (3D) machine vision system that employs optical sensing devices, such as cameras, to determine the positions of various objects. Although such machine vision systems are typically used for alignment purposes, these systems can also be used to obtain other positional and angular orientation information about a motor vehicle. Examples of such apparatus and methods are disclosed in U.S. Pat. No. 5,724,743, entitled xe2x80x9cMethod and Apparatus for Determining the Alignment of Motor Vehicle Wheels,xe2x80x9d issued to Jackson, et al. on Mar. 10, 1998 and in U.S. Pat. No. 5,535,522, entitled xe2x80x9cMethod and Apparatus for Determining the Alignment of Motor Vehicle Wheels,xe2x80x9d issued to Jackson, et al. on Jul. 16, 1996, each incorporated herein by reference. The apparatus disclosed in these patents is sometimes called a xe2x80x9c3D alignerxe2x80x9d or an xe2x80x9caligner,xe2x80x9d hereinafter referred to as a vision imaging system. As used herein, the term xe2x80x9cposition determination systemxe2x80x9d refers to an alignment system, such as the vision imaging system, in addition to other components used in conjunction with the alignment system to obtain positional and angular orientation information about a motor vehicle.
The above-described position determination system provides information, such as the centers of rotation of the vehicle""s wheels, which aids in the wheel alignment of a vehicle. Other positional information, such as ride height, toe curve, tilt angle, and the angular relationship of the body relative to the wheels, can aid a technician in aligning the wheels and also the body of the vehicle. The current position determination system, however, is not capable of obtaining this information. There is, therefore, a need for an improved position determination system capable of obtaining other positional information about a vehicle, such as ride height, toe curve, tilt angle, and the angular relationship of the body relative to the wheels.
This and other needs are met by a target system that can be used with a position determination system in determining the location of a position on a vehicle. The target system includes a target body, one or more target elements, and a point definer. The target elements are disposed on the target body and are detectable by the position determination system. The point definer extends from the target body, and includes a point capable of being located adjacent the position on the vehicle. The position determination system determines a location of the target body after detecting the target elements disposed on the target body. The point on the point definer can also be at a known location from the target body.
In one aspect, the point is at a distal end of the point definer. Also, the point can be at the vertex of a conical projection at the distal end of the point definer. Furthermore, the point definer can include one or more joints, which enable the point to be positioned at a different location relative to the target body, such as one of three positions. The one or more joints can each allow rotation of the point in one or more axis relative to the target body. Also, each joint can include a lock to selectively prevent or allow movement of the point relative to the target body
In another aspect, the target system can include a trigger for operating the detection of the target system by the position determination system. The trigger can be positioned on the target body and is remote from the position determination system. The trigger operates the position determination system by selectively changing the detection by the position determination system of one or more of the target elements. For example, the trigger can be movable between two positions. In a first position, the trigger conceals the one or more target elements from the position determination system, and in a second position, the trigger exposes the one or more target elements to the position determination system.
In a further aspect, the target elements are positioned on a single line along the body, and the single line can be substantially parallel with a longitudinal axis of the target body. Also, the target system can include an attachment device to stabilize the position of the target body relative to the vehicle and to stabilize the point on the point definer relative to the position on the vehicle to be located. The attachment device can include an attachment arm and a connector that detachably connects to the vehicle. The attachment arm is attached to the target body by a first pivot and is attached to the connector by a second pivot.
Alternatively, the attachment device, such as one adapted to be attached to a strut of the vehicle, can include a receiver to which the point definer is attached and a connector that connects with the vehicle. The receiver, such as a cylindrical recess into which a portion of the point definer can be inserted, can include a reference feature, such as a flat plane, that defines the position of the attachment device relative to the point on the point definer. The connector can also define a positional relationship between the position on the vehicle to be located and the reference feature. The combination of the reference feature and the receiver can prevent movement of the point definer relative to the attachment device in three axes.
In another aspect, a method of obtaining a location of a position on a vehicle using a position determination system is provided. The method includes indicating the position with a target system, and imaging the target system with the position determination system to obtain the location. The target system used to indicate the position includes a target body, target elements disposed on the target body and detectable by the position determination system, and a point definer extending from the target body. The point definer includes a point capable of being located adjacent the position on the vehicle. The position determination system calculates the location of the target body and interpolates the location of the point from the location of the target body.
The point can be positionable relative to the target body in one of three point positions. If so, the target system is imaged and the location of the point is interpolated for each point position. The interpolated location of the point for each point position is then compared to an estimated location of the position on the vehicle. The location is obtained by choosing the interpolated location closest to the estimated location.
The target system can trigger the imaging of the target system by the position determination system. In so doing, a trigger can selectively change the detection by the position determination system of one or more of the target elements. For example, the trigger can selectively conceal or reveal one or more target elements respectively from or to the position determination system.
Calibrating the target system involves determining the positional relationship of the point relative to the target body. For example, the target system can be calibrated by positioning the target body of the target system in at least three different locations while fixing the point of the point definer adjacent to the position on the vehicle to be located. The location of the target body at each of the at least three different locations is then determined, and the point of the point definer is interpolated from the at least three different locations of the target body. Alternatively, the target system can be calibrated by positioning the target body of the target system in at least three different locations while maintaining the point definer within a calibration fixture. The location of the target body at each of the at least three different locations is then determined, and the point of the point definer is interpolated from the at least three different locations of the target body
In one aspect, a method of measuring a body tilt angle of a vehicle using a position determination system is provided. The method includes indicating vehicle definition points on the vehicle using one or more target systems, imaging the one or more target systems to obtain a position for each of the vehicle definition points; defining a body tilt line using the positions of each of the vehicle definition points; defining a reference line; and calculating the body tilt angle between the body tilt line and the reference line. The calculated body tilt angle can be then compared to a specified range of body tilt angles.
The reference line can be along the plane defined by the surface upon which the vehicle is supported or along the plane defined by centers of rotation of wheels of the vehicle. The centers of rotation of the wheels are indicated using targets, which are positioned on the wheels and imaged by the position determination system.
The vehicle definition points can include points found on each side of the vehicle, as split by a vertical plane passing centrally through a length of the vehicle. Also, the vehicle definition points of the at least one set of vehicle definition points can be selected from identical locations common to both sides of the vehicle.
In still another aspect, a method of measuring a perpendicular distance on a vehicle using a position determination system is provided. The method includes indicating a reference point on the vehicle with a target system; imaging the target system to obtain a position of the reference point; defining a reference plane; and calculating the perpendicular distance between the reference plane and the reference point. The calculated perpendicular distance can be then compared to a specified range of perpendicular distances, such as ride height.
The reference plane can be defined by the surface upon which the vehicle is supported using at least three non-collinear points, which are indicated using the target system. The reference plane can also be defined by centers of rotation of wheels of the vehicle. The centers of rotation of the wheels are indicated using targets, which are positioned on the wheels and imaged by the position determination system.
In yet another aspect, a method of obtaining a toe curve for a wheel on a vehicle using a position determination system is provided. The method includes indicating a reference point on the vehicle with a target system; imaging the target system to obtain a position of the reference point; defining a reference plane; obtaining a first toe angle of the wheel; calculating a first perpendicular distance between the reference plane and the reference point with the first toe angle and the first perpendicular distance defining a first data point; changing the first perpendicular distance to a second perpendicular distance; obtaining a second toe angle of the wheel with the second toe angle and the second perpendicular distance defining a second data point; and interpolating a toe curve from at least two data points. The toe angles can be obtained by imaging a target positioned on the wheel using the position determination system. The calculated toe curve can be then compared to a specified range of toe curves.
The reference plane can be defined by the surface upon which the vehicle is supported or defined by centers of rotation of wheels of the vehicle. The centers of rotation of the wheels are indicated using targets, which are positioned on the wheels and imaged by the position determination system.
The second perpendicular distance can be obtained by vertically moving the reference point relative to the reference plane followed by imaging the target system again to obtain a second reference point. The second perpendicular distance is then calculated between the reference plane and the second reference point.
A toe angle can be extrapolated from the toe curve for a given perpendicular distance, and the extrapolated toe angle can then be compared to a specified range of toe angles for the given perpendicular distance. Also, a perpendicular distance can be extrapolated from the toe curve for a given toe angle, and the extrapolated perpendicular distance can be compared to a specified range of perpendicular distances for the given toe angle.
In a further aspect, a method of measuring alignment of a body of a vehicle relative to wheels of the vehicle using a position determination system is provided. The method includes indicating a plurality of body definition points on the vehicle with a target system; imaging the target system to obtain positions of the body definition points; calculating a body center line from the positions of the body definition points; obtaining a wheel center line; and calculating a body alignment angle between the body center line and the wheel center line. A calculated body alignment angle can be then compared to a specified range of body alignment angles.
Obtaining the wheel center line involves indicating the centers of rotation of the wheels using targets, which are positioned on the wheels, and imaging the targets with the position determination system to obtain positions of the wheels. In addition, a front center point of a front wheel track extending between the wheel definition points of two front wheels can be calculated, as well as a rear center point of a rear wheel track extending between the wheel definition points of two rear wheels. The wheel center line is then defined as including the front center point and the rear center point.
The plurality of body definition points can include two sets of two body definition points with each set of body definition points including body definition points found on each side of the vehicle, as split by a vertical plane passing centrally through a length of the vehicle. Also, the body definition points of each set of body definition points can be selected from identical locations common to both sides of the vehicle. Still further, the two sets of body definition points can includes a front set substantially adjacent to a front of the vehicle and a second set substantially adjacent to a rear of the vehicle.
Obtaining the body center line further involves calculating a front body center point of a front body line extending between the body definition points of the front set, and calculating a rear body center point of a rear body line extending between the body definition points of the rear set. The body center line is then defined as including the front body center point and the rear body center point.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only an exemplary embodiment of the present invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.